1. Field of the Invention
The present invention relates to a tape measure in which a flexible measuring tape is accommodated inside a case.
2. Description of the Related Art
Tape measures in which a flexible measuring tape is accommodated inside a case have structure in which the flexible measuring tape is accommodated by being wound around the circumference of a take-up drum which is supported inside the case such that this take-up drum is free to rotate. A take-up spring is installed on this take-up drum, and when the measuring tape is pulled out, a spring force is accumulated in the direction in which the measuring tape is retracted. Accordingly, when the hand is released from the measuring tape that has been pulled out, the measuring tape is automatically retracted into the case by the spring force of the take-up spring.
In order to ensure that the measuring tape is completely taken up inside the case, a strong spring that can overcome the frictional force that occurs during take-up is used as the take-up spring. Accordingly, when the measuring tape is rewound after being pulled out a long distance (e. g., approximately 3 m), the take-up speed of the measuring tape increases, so that rebound of the measuring tape occurs, thus leading to the possibility of damage to the measuring tape, or the possibility that the rebounding measuring tape will strike fingers of a user during use.
The tape measure disclosed in Japanese Patent Application Laid-Open Publication No. 8-5301 is a tape measure which suppresses the rise of the rotation speed of the take-up drum, gains large breaking force when the case is turned in a certain direction, and solves such problems.
However, since the braking force of the tape measure depends on the direction, there has been a problem that sufficient force cannot be obtained in a certain condition in which the tape measure is used.
Furthermore, there has been another problem that the measuring tape is inadvertently retracted into the case, when measuring is carried out with the measuring tape kept outside the case.
It is an object of the present invention to provide a tape measure which solves the above problems, and can gain large braking force regardless of the direction of the case.
It is another object of the present invention to provide a tape measure which can prevent inadvertent retraction of the pulled-out measuring tape.
It is still another object of the present invention to provide a tape measure which can suppress the rise in the rotational speed of the take-up drum by a simple mechanism.
According to one aspect of the present invention, there is provided a tape measure which comprises: a take-up drum which is supported by a supporting shafts disposed inside a case such that this take-up drum is free to rotate, and around whose circumference a measuring tape is wound; a take-up spring which urges the take-up drum to move in the retraction direction of the measuring tape; bearings which are formed on the take-up drum, have inner diameters that are larger than the outer diameters of the supporting shafts, and enable the take-up drum to move in the radial direction of the supporting shafts; an operation member which is installed on the case, and moves the take-up drum in the radial direction of the supporting shafts so as to move in one direction of the inside wall of the case; and braking member which is disposed on the inside walls of the case, and applies braking force to the rotation of the take-up drum by making contact with the outer circumference of the take-up drum when the take-up drum is moved by the operation member.
As a result, braking force can be applied by moving the take-up drum in the radial direction of the supporting shafts by means of the operation member so as to make the take-up drum contact with the braking member. Thereby, a sufficient braking force can be obtained regardless of the direction of the case. Furthermore, since the speed of taking up the measuring tape can be suppressed, it is possible to prevent, for example, the damage of the measuring tape caused by abrupt take-up. Moreover, since the take-up drum is caught between the operation member and braking members, sufficient braking force can be obtained by applying small force.
The front surfaces of the braking members may have curved surfaces that generally conform to the outer circumferential form of the take-up drum. In this manner, the contact area between the take-up drum and the braking member can be increased, so that a larger braking force can be obtained.
The operation member may further comprise: a knob member which is located on the side wall of the case (this side wall demarcates the outer circumferential parts of the take-up drum) such that this knob member is free to move to and from the inside of the case; and a brake shoe which is disposed on the knob member and inside the case, and contacts with the outer circumferential parts of the take-up drum so as to cause the take-up drum to move toward the opposite side of the operation member, and also gives braking force to the rotation of the take-up drum. In the tape measure having these elements, it is possible to apply still larger braking force to the take-up drum, because the brake shoe itself also can apply braking force in addition to the braking force applied by pushing the knob member toward the inside of the case so as to make the take-up drum contact with the braking member.
The cross-sectional shape of the supporting shafts may also be a non-circular shape. By making the supporting shafts have such a shape, it is possible to restrict the range within which the take-up drum can move in the radial direction of the supporting shafts, so that the take-up drum does not unnecessarily contact with the inside wall of the case.
According to another aspect of the present invention, there is provided a tape measure comprising: a take-up drum which is supported by supporting shafts disposed inside a case such that this take-up drum is free to rotate, and around whose circumference a measuring tape is wound; a take-up spring which provides impetus causing the take-up drum to rotate in the retraction direction of the measuring tape; bearings which are formed on the take-up drum, have inner diameters larger than the outer diameters of the supporting shafts, and enable the take-up drum to move in the radial direction of the supporting shafts; an operation member which is installed on the case, causes the take-up drum to move in the radial direction of the supporting shafts, and thereby forces the take-up drum to move in one direction of the inside wall of the case; braking members which are disposed on the inside wall of the case, and apply braking force to the rotation of the take-up drum by the contact between the braking members and the outer circumferential parts of the take-up drum when the take-up drum is moved by the operation member; and tape lock means which are disposed in the operation member for fixing the measuring tape in an appropriate place by applying braking force to the measuring tape pulled out of said take-up drum to the outside of said case against the impetus by the take-up spring so as to maintain the length of the pulled-out measuring tape.
As a result, braking force can be applied by moving the take-up drum in the radial direction of the supporting shafts by means of the operation member so that the take-up drum is caused to contact with the braking members. Accordingly, sufficient braking force can be applied without depending on the direction of the case. Furthermore, since the take-up speed of the measuring tape can be suppressed, it is possible to prevent, for example, the damage of the measuring tape caused by abrupt take-up. Moreover, since the take-up drum is caught between the operation member and braking members, it is possible to obtain sufficient braking force by applying a small force. In addition, the measuring tape is not inadvertently retracted during measurement, because the measuring tape can be held in a state in which the measuring tape is pulled out by the measuring tape lock means, so that there is no inadvertent retraction of the measuring tape during measurement. Moreover, the efficiency in measuring is good, because it is possible to hold the measuring tape with arbitrary length of the pulled-out measuring tape.
The measuring tape lock means may include a braking piece which fixes the measuring tape pulled out of the take-up by applying braking force applied by the contact between this lock means and the measuring tape, and hold means for holding the braking piece in a place where the measuring tape should be fixed. In this manner, the hold means enables the braking piece to be held with the measuring tape fixed.
The operation member may include: a knob member which is located on the side wall of said case that demarcates the outer circumferential parts of said take-up drum such that this knob member is free to perform a reciprocating motion to and from the inside of the case; a brake shoe which is located inside said case, contacts with the outer circumferential parts of said take-up drum so as to move said take-up drum toward the opposite side of said operation member, and applies braking force to the rotation of said take-up drum; a braking piece which contacts with one side surface of said pulled-out measuring tape, and thereby applies braking force when said knob member is made to move, along the outer circumferential parts of said take-up drum, toward an opening out for pulling out the measuring tape; and hold means for holding said knob member in the place where said knob member is located, when said braking piece contacts with the one side surface of said measuring tape and thereby applies braking force. By using this operation member having these elements, it is possible to apply braking force to the take-up drum by pushing the knob member toward the inside of the case, and possible to hold the measuring tape with arbitrary length of the pulled-out measuring tape by moving the knob member, along the outer circumference of the take-up drum, toward the opening for the measuring tape.